Proposals have already been made in U.S. Pat. No. 4,390,357 concerning apparatus for removing dust from the atmosphere around a drawing machine for drawing an optical fiber preform, the apparatus setting up a laminar flow of air along successive enclosures surrounding the preform, the bare optical fiber, and then the optical fiber covered with a protective coating. Merely setting up a laminar flow of air over one of the sides of the preform, as described in said document, is not enough to provide adequate protection of a tubular preform while a deposit is being formed therein with the preform being periodically heated from one end to the other, and any impurity contained in the ambient atmosphere may deposit itself on the outside surface of the preform which will give rise to non-uniformities in the structure of the preform and consequently in its mechanical strength.
Preferred implementations of the present invention provide apparatus for removing dust from the atmosphere around a tube, which apparatus is capable of providing substantially complete protection of the outside surface of the tube against any impurity being deposited thereon, and, in the specific case of manufacturing optical fibers by drawing a preform, preferred implementations of the present invention provide an optical fiber having a highly uniform structure.